Paving systems use screeds to heat and compress paving materials, particularly asphalt paving materials. A screed of a paver may be adjustable out to six meters, but often it is desirable to extend the width through the use of extendable screeds. These extensions may add an additional 2 meters on either side of the main screed, for example, using hydraulically adjustable extendable screeds.
The extendable screeds may be mounted to the main screed body, but for various reasons are not usually collinear with the main screed body. For example, the extendable screeds may be mounted behind the main screed. Therefore, when the height of the main screed body is adjusted up or down, or its angle of attack is changed, the extension may move differently than the main body because it has a different radius from a pivot point of the main screed body. Angle of attack is the front-to-back angle of a screed that affects the difference in height above the paving surface of the front of the screed vs. the back of the screed.
Many current systems use a ‘four post’ system for adjusting the height and angle of attack of an extendable screed. However, manually loosening each post, making the adjustment, and re-tightening each post is very time and labor intensive. Other systems may allow the trailing edge of the extendable screed to be manually adjusted, but like the four post system, six or more individual bolts with locking nuts may need to be adjusted to make a change. Both of these adjustment techniques are time consuming and, given the work environment, often hot, dirty, and difficult to work on.
U.S. Pat. No. 6,158,921 discloses a screed extension mounted in front of a main screed body so that a rear-facing side of the extension touches a front-facing side of the main screed body. The distance of the extension from the main body determines where the contact between the two occurs and therefore, the angle of attack of the extendable screed. While the '921 patent discloses both height adjustment and angle of attack adjustment, the angle of attack is directly a function of its height and requires fore-and-aft adjustment for each change in height. The '921 patent does not disclose an extendable screed adjustment system that allows independent height and angle of attack adjustment.